1. Field of the Invention
This invention relates to a door-type rotary nozzle, and more specifically to a door opening/closing device of the door-type rotary nozzle.
2. Description of the Prior Art
Rotary nozzle systems have been used widely with ladles for receiving the molten steel tapped from a converter to transport or pour the molten steel into molds, tundishes for receiving the molten steel from a ladle to pour the molten steel into molds and the like.
Particularly, a door-type rotary nozzle in which a rotor including a slide plate brick are pivoted by hinges so as to open and close these bricks and this type of nozzle has a number of features that the contacting or sliding surfaces of the top nozzle, the bottom plate brick and the slide plate brick can be exposed to permit the confirmation of any damages on the brick surfaces by the naked eye, that there is no need to prepare any standby set for replacing or repairing the bricks, that the operation is easy and so on, has often been used recently.
The door of such a door-type rotary nozzle is pivotably attached with a hinge on a base member fixed to the bottom part of a ladle and opened and closed through this hinge. However, it is necessary to place tightly the bottom plate brick in contact with the slide plate brick at closure to prevent leakage of molten metal and intrusion of air. Also, it is absolutely necessary, for safety, to surely lock it so that it does not open during operation.
One example of such a door-type rotary nozzle is given in the Japanese Laid-Open Patent Application No. 59-107764. To open the door in this door-type rotary nozzle, a clamper is inserted into the portion provided at the upper part of a rotor, and a nozzle hole is set at the fully closed position by rotating the rotor by a 90 degree angle. As a result, a cam intrudes under the clamper and the rotor is pushed down and compresses a coil spring. Therefore, a gap is generated between the bottom plate brick and the slide plate brick, and the door as a whole is pushed down to the part corresponding to this gap. As a result, a lock arm can be easily rotated and unlocked by pushing down a frame on the lock side by hand, and the door can be rotated with the hinge as an axis.
This door-type rotary nozzle has various characteristics and has been widely used in and out of Japan, but the following problems have taken place.
(1) As the clamper is inserted from the side of upper part operators sometimes forget to pull out the clamper to pour in the molten metal, which causes a leakage accident.
(2) As the clamp position is provided on the side of the fixed frame, a holder provided at the ladle interferes in fitting and removing of the clamper.